Amino derivatives of pyrazolopyridine carboxamides

ABSTRACT

1. A COMPOUND OF THE FORMULA   1-R1,3-R2,4-(R3-N(-R4)-),5-(R6-N(-R5)-CO-),6-R7-1H-   PYRAZOLO(3,4-B)PYRIDINE   WHEREIN R1 IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND LOWER ALKYL; R2 IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, LOWER ALKYL AND PHENYL; R3 AND R4 ARE EACH SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, LOWER ALKYL, LOWER ALKENYL, PHENYL SUBSTITUTED PHENYL, PHENYL-LOWER ALKYL, AND DI-LOWER ALKYLAMINO-LOWER ALKYL; R5 AND R6 ARE EACH SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, LOWER ALKYL AND DI-LOWER ALKYLAMINO-LOWER ALKYL; AND R7 IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND METHYL; WHEREIN LOWER ALKYL AND LOWER ALKENYL REFER TO HYDROCARBON GROUPS HAVING UP TO 8 CARBON ATOMS; WHEREIN SUBSTITUTED PHENYL REFERS TO PHENYL SUBSTITUTED WITH 1 TO 2 SUBSTITUENTS SELECTED FROM THE GROUP CONSISTING OF LOWER ALKYL, HALOGEN, TRIFLUOROMETHYL, AMINO AND CARBOXY; AND PHYSIOLOGICALLY ACCEPABLE ACIDADDITION SALTS THEREOF.

United States Patent 3,840,546 AMINO DERIVATIVES 0F PYRAZOLOPYRIDINE CARBOXAMIDES Hans Hoehn, Tegernheim, and Theodor Denzel, Nuremberg, Germany, assignors to E. R. Squibb & Sons, Inc., Princeton, NJ. No Drawing. Filed Nov. 15, 1972, Ser. No. 306,967 Int. CI. (30711 31/44 US. Cl. 260-2955 B 7 Claims ABSTRACT OF THE DISCLOSURE 4-amino derivatives of pyrazolo[3,4- b]pyridine-5-carboxamides having the formula v l -s N-R4 A 0 /R& R i k-N are disclosed. The novel compounds are useful as ataractic, analgesic, and hypotensive agents.

SUMMARY OF THE INVENTION This invention relates to new 4-amino derivatives of pyrazolo[3,4-b]pyridine 5 carboxamides and salts of these compounds. These new compounds have the formula a R N\ \N N R1 is an acyclic amino group wherein R and R may each be hydrogen, lower alkyl, lower alkenyl, lower alkanoyl, phenyl, substituted phenyl, phenyl-lower alkyl, di-lower alkylamino-lower alkyl, benzoyl, substituted benzoyl, phenyl-lower alkanoyl, substituted phenyl-lower alkanoyl, alkanesulfonyl, benz'enesulfonyl, or substituted benzenesulfonyl.

The basic nitrogen group may also be heterocyclic containing 3, 4, 5, or 6 mem bers; an additional hetero atom, e.g. nitrogen, oxygen, or sulfur may be included.

The basic nitrogen group RI N "ice of the carboxamide moiety is an acyclic amino group wherein R and R may each be hydrogen, lower alkyl,

alkoxy lower alkyl, or di-lower alkylamino-lower alkyl.

The basic nitrogen group may also be heterocyclic containing 5, 6, or 7 members; an additional hetero atom, GJgnitrogen, oxygen, or sulfur may be included. The heterocyclic moiety may have one or two simple substituents.

R is hydrogen, lower alkyl, or phenyl.

DETAILED DESCRIPTION OF THE INVENTION The lower alkyl and lower alkenyl groups referred to throughout the specification include straight or branched chain hydrocarbon groups containing 1 to 8 carbon atoms. Examples of the type of group contemplated are methyl, ethyl, propyl, isopropyl, butyl, t-butyl, etc., and corresponding compounds having one double bond.

The lower alkanoyl groups referred to throughout the specification include the acyl radicals of acids having the formula C H COOH wherein n must be 7 or less.

The cycloalkyl groups referred to throughout the specification include the 3 to 7 carbon atom alicyclic groups-cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl. The 5 and 6 membered rings are preferred.

The substituted phenyl, substituted benzoyl and substituted benzenesulfonyl groups referred to throughout the specification may include one or two simple substituents, i.e., lower alkyl, halogen (F, Cl, Br, or I; preferably C1 or Br), trifluoromethyl, amino, or carboxy.

Preferred embodiments of this invention are as follows:

R is hydrogen or lower alkyl, most preferably hydrogen or ethyl.

R is hydrogen or lower alkyl, most preferably hydrogen or methyl.

R is lower alkyl, most preferably butyl.

R is hydrogen.

Alternatively R and R together with the nitrogen to which they are attached, may form a 5 or 6 membered heterocyclic such as pyrrolidino, piperidino, pyrazolyl, pyrimidinyl, pyridazinyl, thiodiazinyl, oxadiazinyl, or azolyl; most preferred of the 5 and '6 membered rings are pyrrolidino, piperidino, and piperazino.

R is lower alkyl, most preferably ethyl.

R is hydrogen or lower alkyl, most preferably hydrogen or ethyl.

Alternatively, R and R together with the nitrogen to which they are attached, may form a 5 or 6 membered heterocyclic; most preferred of the 5 and 6 membered by several methods.

According to one procedure, when R is other that hydrogen, a product of formula 'I may be producedfrom compounds of the formula 3 or from compounds of the formula III 7 V R: I

I R i I b-x or from compounds of the formula /R& R ii-N \N N/ R1 where X is halogen, preferably chlorine or bromine.

The compounds of formulas II, III and IV are formed by the following series of reactions. The symbols in the structural formulas have the same meaning as previously described.

A S-aminopyrazole of the formula E A-N112 l,

prepared according to the procedure described in Z.f. Chemie, 10, 386-388 (1970) is made to react with an alkoxymethylene malonic acid ester of the formula by heating at a temperature of about 120 C.

The resulting compound of the formula VII I0 undergoes cyclization in an inert organic solvent such as diphenyl ether at about 230 to 260 C., while distilling off the alcohol formed, producing a compound of the formula VIII 0H The resulting compounds of formulas VIII and IX are saponified by means of sodiumor potassium hydroxide at room temperature providing the corresponding free acids, which in turn are converted by refluxing with thionylchloride to the intermediate of formula H wherein X will be C1.

The product of formula I is then prepared from a compound of formula II by reaction with the appropriate primary or secondary amine of the formula and the formula The reaction for introducing the amino group in position 4 as well as in the carboxamide moiety in position 5 can be effected in either one or two steps. Preferred, however, is the two step reaction, because it allows one to prepare derivatives of formula I bearing different amines in the 4 position and as part of the carboxamide moiety. At lower temperatures, e.g., in the range of 0 to 10 C. the compound of formula II reacts with the amine of formula X to furnish the intermediate of formula IV which in turn reacts with compounds of formula XI at room temperature providing the amino derivatives of pyrazolo[3,4 blpyridine-S-carboxamides of formula I.

Alternatively, instead of saponification of the ground of formula IX as described above, this product can be converted to the compound of formula by reaction with the amine of formula XI. The subsequent saponification of the ester of formula XII yields the free acid, which in turn is converted to the acid chloride of formula III. Aminolysis with amines of formula X furnishes the amino derivative of pyrazolo[3,4-b]- pyridine-S-carboxamide of formula I. In some cases the direct conversion of the ester to the carboxamide group may be possible and advantageous.

According to a modification of the foregoing procedure, a product of formula I wherein R is hydrogen may be produced. By this modification, a S-aminopyrazole of formula IV wherein R is an arylmethyl group or a heteromethyl group is used. This starting material has the formula I CH1 wherein R is an aromatic or heterocyclic nucleus like phenyl, naphthyl, furyl, pyridyl, pyrimidyl, pyrazinyl or the like.

This material is processed as described above through the reaction with the alkoxymethylene malonic acid ester of formula VI, cyclization of the product corresponding to formula VII to obtain a compound of formula VIII, with a hydroxy group in the 4-position, and then alkylating to obtain a compound of formula At this point, the compound of formula XIV having in the 1-position the R CH substituent is oxidized with an oxidizing agent like selenium dioxide in a high boiling solvent like diethyleneglycol dimethylether at about 160 yielding the compound of the formula C-O-alkyl wherein R is hydrogen.

The subsequent treatment of the ester of formula XV with the amine of the formula XI provides the compound of the formula XII, which in turn is converted via the acid and acid chloride to the amino derivative of pyrazolo[3,4-b]pyridine-S-carboxamide of formula I. Sometimes it may be advantageous to convert the ester of formula XII directly to compound of formula I by means of reacting the ester group with the amine of formula X at elevated temperatures.

The compounds of formula I form salts which are also part of this invention. The salts include acid-addition salts, particularly the non-toxic, physiologically acceptable ones. The bases of formula I form acid-addition salts by reaction with a variety'of inorganic and organic acids. Examples of acid-addition salts are the hydrohalidcs (especiallythe hydrochloride), sulfate, nitrate, phosphate, oxalate, tartrate, malate, citrate, acetate, ascorbate, succinate, benzenesulfonate, toluenesulfonate, cyclohexanesulfonate, cyclohexauesulfamate, etc. The acid-addition salts frequently provide a convenient means for isolating the product, e.g., by'forming and precipitating the salt in an appropriate menstruum in which the salt is insoluble, then after separationof the salt, neutralizing with a base such as barium hydroxide or sodium hydroxide, to obtain the free, base of formula 1. Other salts may then be formedfrom the free base by reaction with an equivalent of acid.

The novel compounds of this invention are central nervous system depressants andare useful as ataractic agents. They find further utility as analgesic and hypotensive agents. They may be used, for example, in mice, cats, rats, dogs and other mammals. For, this purpose, a compound or mixture of compounds of formula I, or non-toxic, physiologically acceptable acid addition salts thereof, may be administered orally or parenterally in a conventional dosage form such as tablet, capsule, injectable or the like. A single dose, or preferably 2 to 4 divided doses may be provided on a basis of about 1 to 50 milligrams per kilogram per day, preferably about '2 'to .15, mg./kg./day. These may be conventionally formulated in an oral or parenteral dosage form by compounding about to 25 milligrams per unit of dosage with conventional vehicle, excipient, binder, preservative stabilizer, flavor or the like as called for by accepted pharmaceutical practice.

The following examples are specific embodiments of the invention. All temperatures are recorded on the centigrade scale.

EXAMPLE 1 4-butylamino-l-ethyllH-pyrazolo[3,4-b]pyridine- 5 (N-butyl) carboxamide, hydrochloride (a) [[(1 ethyl-S-pyrazolyl)amino]methylene]malonic acid diethyl ester.245 g. of l-ethyl-S-aminopyrazole (2.2 mol) and 476 g. of ethoxymethylene malonic acid diethyl ester (2.2 mol) are heated to 120 (bath temperature) for 2 hours with stirring. The ethanol formed by this reaction is removed by means of a water aspirator. Vacuum distillation (bp 154-160") yields 520 g. (84% of theory) of a quickly crystallizing oil of l-ethyl 5 pyrazolyl)amino] methylene] malonic acid diethyl ester, m.p. 50-53". The compound is recrystallized from N-hexane, and has a melting point of 55-57".

(b) 1-ethyl-4-hydroxy 1H pyrazolo[3,4-b]pyridine- S-carboxylic acid ethyl ester.253 g. of [[(1-ethyl-5- pyrazolyl)amino]methylene]malonic acid diethyl ester (0.09 mol) is dissolved in 770 g. of diphenyl ether. The reaction mixture is heated to 235250 (bath temperature) and allowed to react at this temperature for 1 to 2 hours, while the resulting ethanol is continuously distilled off. The remaining alcohol is removed by means of a water aspirator. The diphenyl ether is separated by distillation with a fractionating column in vacuo. The 1-ethyl-4-hydroxy 1H pyrazolo[3,4-b1pyridinecarboxylic acid ethyl ester is obtained at b.p. 115120, yield 195 g.=92% of theory, m.p. 86-87. The compound is recrystallized from ligroin (90 to and has a melting point of 8789.

(c) l-ethyl 4 hydroxy-lH-pyrazolo[3,4-b]pyridine- S-carboxylic acid.47 g. of l-ethyl-4-hydroxy-lH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (0.2 mol) are saponified by means of 400 ml. of aqueous sodium hydroxide (2.5 N) by refluxing the mixture for 1 /2 hours. After cooling of the filtered solution and diluting with 300 ml. of water, it is acidified with glacial acetic acid.

' The precipitated l-ethyl-4-hydroxy-lH-pyrazolo[3,4-b]

pyridine-S-carboxylic acid is filtered under suction, washed with water and dried at Yield 37 g. (89%), recrystallization from glacial acetic acid, and has a melting point of 201-202".

(d) 4 chloro l ethyl-lH-pyrazolo[3,4-b1pyridine- S-carbonyl chloride.A mixture of 31 g. of 1-ethyl-4-hydroxy-lH-pyrazolo[3,4-b]pyridine 5 carboxylic acid (0.15 mol) and ml. of thionylchloride is heated under reflux for 4 hours. Then the thionylchloride is evaporated completely in vacuo; the oily residue (33 g.) which crystallizes quickly is used without purification for the next reaction step.

(e) 4-butylamino l-ethyl-lH-pyrazolo[3,4-b]pyridine- 5-(N-butyl)carboxamide, hydrochloride.-To a solution of 24.4 g. of 4-ohloro-l-ethyl-lI-I-pyrazolo[3,4-b]pyridine- S-carbonylchloride (0.1 mol) in 75 ml. of dry benzene, 32 g. of n-butylamine (0.44 mol) dissolved in 75 ml. of benzene is slowly added with cooling. The reaction mixture is allowed to remain at room temperature while stirring for 6 hours, during which time a precipitate forms. The mixture is evaporated to dryness in vacuo. The residue is washed with water, filtered under suction and dried in a desiccator over phosphorous pentoxide. 4-butylamino-l-ethyl-1H-pyrazolo[3,4-b]pyridine 5 (N-butyl) carboxamide (26 g.=82%) is recrystallized from ligroin, and has a melting point of 98-99. The hydrochloride is formed by adding ethereal hydrogen chloride solution to a cooled solution of the carboxamide in ethylacetate. The precipitate is recrystallized from absolute alcohol, and has a melting point of 236-237 decomp.

7 EXAMPLE 2 1-ethyl-3-methyl-4-( l-piperidino)-1H-pyrazolo[3,4-b]

pyridine-5-(N-piperidyD-carboxamide (a) [[(l-ethyl 3 methyl-S-pyrazolyl) amino]methylene]malonic acid diethyl ester.l2.5 g. of 1-ethyl-3- methyl-S-aminopyrazole (0.1 mol) and 21.6 g. of ethoxymethylene malonic acid diethyl ester (0.1 mol) are heated to 120 (bath temperature) for 2 hours with stirring. The ethanol formed by this reaction is removed by means of a water aspirator. Vacuum distillation (b.p. 152-153) yields 24.0 g. (81.5% of theory) of a quickly crystallizing oil, (1-ethyl-3-methyl-5-pyrazolyl)-amino]methylene]malonic acid diethyl ester, m.p. 60-67". The product, recrystallized from ligroin (90-100"), melts at 69-70.

(b) l-ethyl 4 hydroxy-3-methyl-lH-pyrazolo[3,4-b] pyridine-S-carboxylic acid and ethyl ester.-l4.8 g. of [[(l-ethyl B-methyl 5 pyrazolyl)amino]methylene] malonic acid diethyl ester (0.05 mol) is dissolved in 50 g. of diphenyl ether. The reaction mixture is heated to 235-250 (bath temperature) and allowed to react at this temperature for l to 2 hours, while continuously distilling olf the resulting ethanol. The last part of the alcohol is removed by means of a water aspirator. The diphenyl ether is separated by distillation with a fractionation column in vacuo. The 1-ethyl-4-hydroxy-3-methyl-lH-pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester is obtained at b.p. 125-129, yield 10.7 g.=86% of theory, m.p. 91-93 The compound is crystallized from ligroin (90-100"), and has a melting point of 93-94. Hydrolysis of this product with aqueous sodium hydroxide yields l-ethyl-4-hydroxy-3-methyllH-pyrazolo- [3,4-b]pyridine-S-carboxylic acid, m.p. 212-213.

(c) 4 chloro-l-ethyl 3 methy1-1H-pyrazolo[3,4-b] pyridine-S-carbonyl chloride.-22 g. of 1-ethyl-4-hydroxy- 3-methyl-1H-pyrazolo[3,4-b]pyridine 5 carboxylic acid (0.1 mol) and 75 ml. of thionyl chloride are refluxed for 4 hours. The clear thionyl chloride solution is evaporated to dryness in vacuo. The residue, weighing 24 g. (93% of theory), contains the crude 4-chloro-1-ethyl-3-methyllH-pyrazolo[3,4-b1pyridine-5-carbonyl chloride, which can be used without further purification for the next reaction step. A sample recrystalized from cyclohexane melts at 68-70".

((1) l-ethyl 3 methyl-4-(l-piperidino)-1H-pyrazolo- [3,4-b]pyridine 5 (N-piperidyl)-carboxamide.To a solution of 7.7 g. of 4-chloro-1-ethyl-3-methyl-lH-pyrazolo[3,4-b]pyridine-5-carbonyl chloride (0.03 mol) in 100 ml. of dry benzene, 11.2 g. of piperidine (0.144 mol) is added dropwise. The mixture is stirred at 50 (bath temperature) for 3 hours. After filtering the precipitated piperidine hydrochloride under suction the benzene filtrate is evaporated in vacuo, and the remaining oil is treated with water and then extracted with ether. The ethereal solution is dried over sodium sulfate and filtered. Addition of ethereal hydrogen chloride precipitates the hydrochloride of the 1-ethyl-3-methyl-4-(l-piperidino)- lH-pyrazolo[3,4-b1pyridine 5 ('Npiperidyl)-carboxamide, which is filtered under suction and recrystallized from a mixture of ethyl acetate and absolute alcohol (1:1). Yield 9.2 g. (78.6%), m.p. 197-199 decomp.

EXAMPLE 3 4-amino- 1-ethyl-3-methyl-1H-pyrazolo [3 ,4-b] pyridine-5- (N-2,2-diethoxyethyl) -carboxamide (a) 4 chloro 1 ethyl-3-methyl-1H-pyrazolo[3,4-b] pyridine-5-(N-2,2 diethoxyethyl)carboxamide.l5.5 g. of 4-chloro 1 ethyl-3-methyl-lH-pyrazolo[3,4-b]pyridine-5carbonyl chloride (0.06 mol) dissolved in 200 ml. of dry ether is cooled to a temperature of 2". By adding a solution of 16 g. of aminoacetaldehyde-diethylacetal (0.12 mol) in 75 ml. of dry ether dropwise to the reaction mixture while stirring, the internal temperature rises to 18 within 20 minutes. Stirring is continued for an additional 20 minutes at room temperature. The precipitate is filtered under suction, washed with ether and suspended in about ml. of water. After vigorous stirring, the crude product is again filtered under suction, washed with water and dried over phosphorous pentoxide in a desiccator. Yield 15.5 g. (73%), m.p. 121-123. Recrystallization of the 4-chloro-1-ethyl-3-methyl-lH-pyrazolo- [3,4 b] pyridine 5 (N-2,2-diethoxyethyl)carboxamide gives a compound with a melting point of 123-125 A further crop of 3 g. is obtained by Working up of the mother liquor.

(b) 4-amino 1 ethyl-3-methyl-lH-pyrazolo[3,4-b] pyridine-S-(N-2,2-diethoxyethyl)carboxamide.3.5 g. of 4-chloro 1 ethyl-3-methyl-1'H-pyrazolo[3,4-b]pyridine- S-(N-diethoxyethyl)carboxamide (0.01 mol) and 60 ml. of alcoholic ammonia (about 65 g./l.) are heated to 125- (bath temperature) in an autoclave for 7 hours. Subsequently, the alcohol is removed in vacuo and the residue is treated with 'water, filtered under suction and dried over phosphorous pentoxide in a desiccator. 2.7 g. (80.6%) of 4-amino-l-ethyl-3-methyl-1H-pyrazolo[3,4- b]pyridine 5 (N-2,2-diethoxyethyl)carboxamide are obtained, m.p. 151-153. Recrystallization from benzene lets the melting point rise to l55-157.

EXAMPLE 4 4-butylaminol-ethyl- 1 H-pyrazolo [3 ,4-b pyridine-5- (N-pyrrolidyl) carboxamide, hydrochloride (a) 4-chloro 1 ethyl-1H-pyrazolo[3,4-b] pyridine-5- carboxylic acid ethyl ester.--A mixture of 12 g. of [[(1- ethyl-S-pyrazolyl)amino]methylene]malonic acid diethyl ester (0.043 mol), obtained as in Example 1(a), and 70 ml. of phosphorus oxychloride are refluxed for 10 hours. The excess phosphorus oxychloride is removed in vacuo and the oily residue is treated with 50 ml. of water which causes the oil to become crystalline. The solid material is filtered off under suction and dried in a desiccator; yield 8.5 g.=79% of theory. The 4-chloro-l-ethyl-lH-pyrazolo- [3,4-b]pyridine-S-carboxylic acid ethyl ester is recrystallized from N-hexane, m.p. 62.

(b) 4-butylamino 1 ethyl-lH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester.To a solution of 5.08 g. of 4-chloro-l-ethyl-lH-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.02 mol) in 20 ml. of benzene is added 2.92 g. of n-butylamine (0.04 mol). This mixture is kept at room temperature for 3 days. After this time, the separated butylamine hydrochloride is filtered under suction and the filtrate is evaporated in vacuo to dryness. The residue, 4-butylamino-1-ethyl-lH-pyrazolo- [3,4-b]pyridine-S-carboxylic acid ethylester, is recrystallized from hexane, m.p. 82-83". The total yield amounts to 5.3 g.=91.5 of theory.

(0) 4-butylamino 1 ethyl-lH-pyrazolo[3,4-b]pyridine-5-carboxylic acid.29' g. of 4-butylamino-1-ethyllH-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.1 mol) is hydrolyzed with 600 ml. of aqueous sodium hydroxide (0.8 N) at 60-70 (bath temperature) with stirring for 14 hours. After acidification with hydrogenchloride, 25.5 g. of 4-butylamino l-ethyl-lH-pyrazolo- [3,4-b]pyridine-5-carboxylic acid, m.p. 208-210 (yield 97%) are obtained. The compound is recrystallized from ethanol, and has a melting point of 213-214.

(d) 4 butylamino l-ethyl 1H pyrazolo[3,4 b] pyridine-S-carbonyl chloride.-26.2 g of 4-butylamino-1- ethyl-1H-pyrazolo[3,4-b]pyridine-S-carboxylic acid (0.1 mol) and 100 ml. of thionyl chloride are refluxed for 4 hours. The thionyl chloride is removed by means of a water aspirator. The residue, containing the crude 4- butyl-amino-l-ethyl-lH-pyrazolo[3,4-b1pyridine 5 carbonyl chloride, is recrystallized from benzene, and has a meting point of l42l45. Yield 23.5 g.=84% of theory.

(e) 4-butylamino 1 ethyl 1H pyrazolo[3,4-b]pyridine-S-(N-pyrrolidyl)carboxamide, hydrochloride.22.4 g. of 4-butylamino-l-ethyl-lH-pyrazolo[3,4-b]pyridine-5- carbonyl chloride (0.08 mole) is dissolved in 100 ml. of dry chloroform. To the solution is added first 8.0 g. of triethylamine and subsequently, while stirring, 12.5 g. of pyrrolidine in 50 ml. of chloroform drop by drop. Stirring is continued at room temperature for 2 hours. The reaction mixture is then evaporated in vacuo to dryness and the residue is treated with 150 ml. of water. The remaining oil is extracted with 150 ml. of ether, the ethereal solution is washed twice with water and then dired; over sodium sulfate. Adding ethereal hydrogen chloride to the dried and filtered solution precipitates the 4 butylamino 1 ethyl 1H pyrazolo[3,4 b]pyridine- 5-(N-pyrrolidyl)-carboxamide, hydrochloride, which after filtering under section is recrystallized from a mixture of ethy acetate and absolute alcohol (6:1). Yield 19.7 g. (70.3%), mp. 170-172".

EXAMPLES 5-8 The following additional compounds are produced by the foregoing procedures having the following formula:

tassium carbonate (1.5 mol) and 233 g. of ethyl iodide are added. The mixture is heated at 60 with continuous stirring for 10 hours. The excess potassium carbonate is filtered oif. On addition of 500 ml. of water, 4-ethoxy-1- (2 furyl)methyl 1H pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester precipitates and is recrystallized from methanol, yield 280 g. (85% m.p. 9396 (d) 4 ethoxy-lH-pyrazolo[3,4-b]pyridine carboxylic acid ethyl ester.3l.5 g. of 4-ethoxy-1-(2-fury1)methyllH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (0.1 mol) and 20 g. of selenium dioxide (0.18 mol) are suspended in 100 ml. diethyleneglycol dimethylether. The mixture is heated with stirring at 160 and a few drops of water are added. The temperature is held steady for 1.5 hours. After cooling, 100 ml. of water is added and the mixture is neutralized with a dilute solution of aqueous ammonia. Yellow crystals are formed, which yield on recrystallization from methanol 15.8 g. of 4 ethoxy-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (67%), mp. 180

(e) 4 butylamino 1H pyrazolo[3,4-b]pyridine-5 carboxylic acid ethyl ester.2.35 g. of 4-ethoxy-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (R5 and Rs form heterocyclie with N). [(R; and R4 form heterocyelic with N).

EXAMPLE 9 4- -butylamino-1H-pyrazolo[3,4 b]pyridine-5-N,N-

. dietheyl-carboxamide (2 furyl) i nethyl 5 pyrazolyl] amino]methylene] malonic acid di'ethyl ester, is recrystallized from methanol, yield 280 g. (84% m.p. 84-86". i

(b) 4 hydroxy 1 (2 furyl)methyl 1H pyrazolo- [3,4-b]pyridine-S-carboxylic acid ethyl ester.250 g. of [[['1 (2 furyl)methyl 5-pyrazolyl]amino]methylene]- malonic acid diethyl ester (0.75 mol) is dissolved in 1 liter of diphenyl ether and heated to 240 for 2 hours. The ethanol formed is continuously distilled off. The solvent isiremoved., -in"vacuo. The 4-hydroxy-1-(2-furyl)methyll'H-pyraz olo[3,4-b]pyridine-S-carboxylic acid ethyl ester remains and is recrystallized from methanol, yield 248 g. (86%),m.p;.103106. f

(c) 4 ethoxy 1 (2-Ifuryl)methyl 1H pyrazolo [3,4-b]pyridine-S-carboxylii: acid ethyl ester.300 g. of 4 hydroxy 1 (2;- furyl)methyl 1H pyrazolo[3,4- b]-pyridine-5-carboxylic acid ethyl ester (1.05 mol) is dissolved in 1 -liter of dimethylformamide. 210 g. of po- (0.01 mol) is treated with 2.2 g. of butylamine (0.03 mol) at for 1 hour. After this period the mixture is cooled, diluted with 20 ml. of water and the White crystalline precipitate is filtered ofi. Recrystallization from diethylether yields 1.7 g. of 4-butylamino-1H-pyrazolo [3,4-b]pyridine-S-carboxylic acid ethyl ester (72% mp. 181. (f) 4 butylamino -1.H- pyrazolo[3,4-b]pyridine-5- carboxylic acid.2.6 g. of 4-butylamino -1H-pyrazolo- [3,4-b]pyridine-S-carboxylic acid ethyl ester (0.01 mol) is treated with 1.1 g. of sodium hydroxide in 30 ml. of ethanol for 20 hours at room temperature. The solvent is removed in vacuo and the residue in dissolved in 10 ml. of waterJOn acidification with acetic acid 4-butylamino- 1H-pyrazolo[3,4-b]pyridine-S-carboxylic acid solidifies and is filtered off. The product is purified by recrystallization from acetic acid, yield 1.9 g. (82%), m.p. 225

(g) 4 butylamino 1H pyrazolo[3,4-b]pyridine-5- N,N-diethylc'arboxamide.2.3 g. of 4-butylamino-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid (0.01 mol) is refluxed with 10 ml. of thionyl chloride for 5 hours. After this time the excess of thionyl chloride is removed in vacuo, the residue dissolved in 20 ml. of dry tetrahydrofuran, and 2 g. of di-ethylamine is added under cooling. The mixture is allowed to stand for 24 hours, then the solvent is evaporated to dryness and 20 ml. water is added to the residue. The crystalline 4-butylamino-1H- pyrazolo[3,4-b]pyridine 5 N,N-diethyl-carboxamide is filtered and recrystallized from acetic acid ethyl ester, yield 2.1 g. 70% m.p.

(a) [[[1-(4-picolyl) pyrazolyl]amino] methylene] malonic acid diethl ester.-174 g. of l-(4-picolyl)-5-aminopyrazole and 216 g. of ethoxymethylene malonic acid diethyl ester are heated with stirring at 140", until the theoretical amount of alcohol has distilled off. The reaction mixture crystallizes on cooling. Recrystallization from ethyl acetate yiel-ds 220 g. of [[[l-(4-picolyl)-5- pyrazolyl] amino]methylene]malonic acid diethyl ester (65%), mp. 95-97". 5

(b) 4-hydroxy 1 (4-picolyl) 1H pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester.86 g. of [[[1-(4- picolyl)-5-pyrazolyl]amino]methylene]malonic acid diethyl ester (0.25 mol) is heated at 240 for 15 minutes. The dark oil is cooled and 200 ml. of methanol is added. 4-hydroxy-l-(4 picolyl) 1H pyrazolo[3,4-b]pyridine- 5-carboxylic acid ethyl ester crystallizes on standing, yield 33 g. (44%), mp. 140.

(c) 4 hydroxy 1H pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester.3 g. of 4-hydroxy-1-(4-picolyllH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (0.01 mol) is dissolved in 20 ml. of acetic acid. 2.2 g. of selenium dioxide (0.02 mol) and 2-3 drops of water are' added. The mixture is refluxed for 30 minutes and then filtered off. 4-hydroxy-1H-pyrazolo[3,4 bJpyridine-S-carboxylic acid ethyl ester precipitates on cooling. Recrystallization from acetic acid yields 1.8 g. (87%.), m.p. 275.

(d) 4-ethoxy 1H pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester.-4.l g. of 4-hydroxy-1H-pyrazolo- [3,4-b]pyridin-e-S-carboxylic acid ethyl ester (0.02 mol), 5.6 g. of potassium carbonate (0.04 mol) and 3.5 g. of ethyl iodide (0.022 mol) are heated in 30 ml. of dirnethylformamide with stirring for hours at 60. After this time, the excess potassium carbonate is filtered OE and 30 ml. of water is added. 4-ethoxy-1H-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester precipitates and is recrystallized from methanol, yield 2 g. (42.5%), m.p. 180. 3 (e) 4-butylamino-lH-pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester.4-ethoxy-lH-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester is treated with butylamine at 90 for 1 hour. After this period the mixture is cooled, diluted With Water and the white crystalline precipitate is filtered ofl. Recrystallization from diethyl ether yields 4-butylamin'o-1H-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester.

(f) 4 butylamino 1H pyrazolo[3,4-b]pyridine-5 carb'oxylic' acid.4-butylamino 1H 'pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester is treated with sodium hydroxide in ethanol for 20 hours at room temperature. The solvent is removed in vacuo and the residue is dissolved in Water. On acidification with acetic acid, 4- butylamino-lH-pyrazolo[3,4-b]pyridine 5 carboxylic acid solidifies and is filtered off. The product is purified by recrystallization from acetic acid.

(g) 4-butylamino-1H-pyrazolo[3,4-b]pyridine 5 N- butyl-carboxamide.4.6 g. 4-butylamino 1H pyrazolo- [3,4-b]pyridine-S-carboxylic acid (0.02 mol) is refluxed with 20 ml. thionyl chloride for 5 hours. The excess of thionyl chloride is removed in vacuo and the residue is dissolved in 40 ml. dry tetrahydrofur-an. 3 g. of n-butylamine is added drop by drop under cooling and the mixture is-stirred at room temperature for 24 hours. Then the solvent is evaporated and 20 ml. of water is added to the residue. The crystalline 4-butyl-amino-lH-pyrazolo- [3,4 b]pyridine-S-N-butyl-carboxamide is filtered off, and recrystallized from methyl alcohol. Yield 4.2 g. (73%), m.p. 227-228".

EXAMPLES '1 l-41 The following additional compounds are produced by the foregoing procedures having the following formula:

Example -crn v mo -mo m ANO NO WO HHO mo mo mo m m v L o H. mo mo mo m m w smgval nmol v nmol NO NO UJQOQHO H IELE Z mmo mu oEoEu mo mo zz mov 50 50 WO NO md Q w o -n q H -mm 1m.. A! 561 1 8 m :w m o z mo fio E6 a m mm m a m o 8 e mo mo 2 mo mo 8 mo mo mo 2 What we claim is:

w E O HHEH f Oi 2 UNITED STATES j PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 840 546 Dated October 8 1974 Inventor) Hans Hoehn and Theodor Denzel It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, lines 42 to 50, formula VII, that portion reading:

II R II V R I II should be: 2 l ll Column 4, line'32, insert a hyphen after [3,4

Column 4, line 33, the word "ground" should be compound v Column 6, line 34, that portion that reads: 8687 should Column 7, line 30, the word "crystal" should be: recrystal- Column 7, line 44, the word "recrystalized" should be:

- recrystallized Column 8, line 74, the word "meting" should be: melting Column 9, line 13, the word "dired" should be: dried Column 9, line 17, the word "section" should be: suction Column 9, line 18, the word "ethy" should be: ethyl Column 9, line 50, title of Example 9, the word "dietheyl" should be: diethyl FORM PO-IOSO (10-69) Y v uscoMM Dc 603766 u. s. sbvsnnusur manna orrlc: nu osu -au,

- it 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION- Patent No; 3,840,546 Dated October 8, 1974 Q lnventofls) Hans Hoehn and Theodor Denzel It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 11, line 5, the word "diethl should be: diethyl Column 13, Example 23, ColumnR should read:

.-- CH -CHN I v Signed and sealed this 24th day of December 1974.

(SEAL) Attest:

r-zccoy M'. GIBSON JR. 0. MARSHALL DANN Y Attesting Officer Commissioner of Patents FORM po'wso (10439) USCOMM-DC we're-Pas ".5. GOVERNMENT PRINTING OFFICE Z I. 0-866-334. 

1. A COMPOUND OF THE FORMULA 